Restructure the entire editor codebase to consistently match the message hierarchy

Closes #744

editor/src/messages/dialog/dialog_message.rs

@@ -0,0 +1,37 @@
+use super::export_dialog::ExportDialogMessage;
+use super::new_document_dialog::NewDocumentDialogMessage;
+use crate::messages::prelude::*;
+
+use serde::{Deserialize, Serialize};
+
+#[remain::sorted]
+#[impl_message(Message, Dialog)]
+#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+pub enum DialogMessage {
+	// Sub-messages
+	#[remain::unsorted]
+	#[child]
+	ExportDialog(ExportDialogMessage),
+	#[remain::unsorted]
+	#[child]
+	NewDocumentDialog(NewDocumentDialogMessage),
+
+	// Messages
+	CloseAllDocumentsWithConfirmation,
+	CloseDialogAndThen {
+		followups: Vec<Message>,
+	},
+	DisplayDialogError {
+		title: String,
+		description: String,
+	},
+	RequestAboutGraphiteDialog,
+	RequestAboutGraphiteDialogWithLocalizedCommitDate {
+		localized_commit_date: String,
+	},
+	RequestComingSoonDialog {
+		issue: Option<i32>,
+	},
+	RequestExportDialog,
+	RequestNewDocumentDialog,
+}